The present invention relates to a pneumatic vehicle tire having a carcass that is looped about two bead cores that comprise load-carrying members such as plastic filaments and/or metal wires, with the beads in which the bead cores are disposed being capable of turning from a vulcanizing position into an operating position when the tire is being mounted on a wheel rim.
A pneumatic vehicle tire of this general type is disclosed in U.S. Pat. No. 4,597,426, Gerhard Mauk et al, issued Jul. 1, 1986 and belonging to the assignee of the present application. This patent indicates that the bead can be rotated about a certain angle that depends upon the properties of the material and the construction of the bead core and the remainder of the bead. Finally, to facilitate the rotational movement of the bead about the bead core, this patent proposes that the bead core be embedded in the bead in a nonadhesive manner, for example by being wound with an appropriately treated strip of fabric.
The aforementioned measures do in fact reduce the resistance of the beads toward turning to such an extent that a mounting process is possible that does not require large recessed mounting portions. Unfortunately, the fatigue strength of these beads, and the true running of the tires provided therewith, leaves much to be desired.
German Offenlegungsschrift 3440440 discloses a bead core with a central member and a plurality of outer members situated therearound. However, the wires of at least the outer layer of members are firmly bonded together, thereby not allowing rotation of each individual member relative to the surrounding bead rubber. Such a construction places too much stress on the bead core.
German Offenlegungschrift 2026875 discloses a bead core comprised of several strands. Unfortunately, the outer layer of strands is provided with a coating of copper, which enhances bonding between these strands and the surrounding rubber. Thus, this construction resists rather than facilitates the ability of the beads to turn when the tire is being mounted on a wheel rim.
It is an object of the present invention to overcome the problems caused by insufficient fatigue strength of the bonding of the outer wires of the beads while at the same time enhancing the ability of the beads to turn.